I bought my sons first bike from Atomic, It arrived with both tubes rooted, sure they said they would replace them free, as long as I sent the stuffed ones back via Aus Post (at my expense). So replacement isn't exactly free. and it wasn't even out of the box let alone 2-3 months old.
At the end of the day it doesnt matter where you get ur bikes from, whether it be off ebay or from a shop, they ALLcome from 1 of half a dozen factories in China.
As long as your happy with your supplier (retailer) all is good..